This invention is directed to a truck trailer brake airline lock where a valve in the air line in the trailer has a lock thereon so that when the brakes are applied, the air line is maintained at the brake-on pressure. In most cases, this is an elevated pressure because in most systems pressure in the air line causes brake actuation.
Trailers and semi-trailers are used for the transport over the highways of much merchandise of modern commerce. The trucks which pull these trailers and semi-trailers are usually provided with an air brake system where air under pressure is supplied to an air line. The air line has a diaphragm which, when actuated, applies the brakes. Usually the mechanism is such that when air pressure rises in the line, the brakes are actuated. Furthermore, in modern systems the air line parts of the brake system are duplicated so that should there be a failure, some braking can still be achieved.
When a trailer or semi-trailer loaded with cargo is parked, it is susceptible to theft by the simple attachment of a new truck, which supplies the braking needs. In order to inhibit theft of the trailer and its cargo, a brake air line locking valve is required.
While locking valves are known, an organization suitable for use on a trailer to lock the trailer brakes in the absence of the truck has not been taught. Maxwell, U.S. Pat. No. 3,998,495 teaches a structure where a separate parking brake system in a truck can be locked from the driver's position. The teaching of that patent is for a separate air brake system, but not for trailer usage. Similar, Cvetkovich, U.S. Pat. No. 3,682,195 locks a hydraulic braking system with a key at the driver's position. Neither of those patents has a significant teaching for trailers. Polit, U.S. Pat. No. 3,362,426 is concerned with anti-theft features and provides a lockable turnoff valve in the conventional hydraulic brake system of an automobile. As an alternative, this valve could be employed in the fuel system. Also in the background is Burdett, U.S. Pat. No. 600,944 which teaches the operating together of a pair of steam valves. None of this art teaches the need for locking the brake system on a trailer or the combination of structure by which it can be accomplished.